Protective head gear are manufactured for: competitive sports, such as football; recreational activities, such as climbing; operation of vehicles, such as motorcycles, bicycles, auto racing, etc.; hazardous industrial environments, such as construction, lumbering, and earth moving; the military; aviation; and fire fighting.
Protective headgear for the foregoing activities usually comprises a rigid outer shell of metal or plastic and a suspension system which supports the shell on the wearer's head in a manner which attenuates impact force and distributes the force which is transferred to the head with the purpose of preventing the impacting object from contacting the head and reducing to a tolerable level the acceleration of the head resulting from the impact.
Impact attenuation suspensions principally take the form of a web of straps attached to the shell and arranged as a cradle over the top of the wearer's head, or take the form of a compressible foam liner which occupies most of the space between the wearer's head and the interior of the shell. The familiar "hard hat" of a construction worker is an example of a web suspension whereas motorcycle helmets usually employ foam liners for impact attenuation.
Web suspensions provide better protection than do foam lined helmets for a vertical blow on the top or apex of the helmet. Foam lined helmets provide better attenuation of lateral impacts than do web suspensions. Consequently, activities more likely to occasion lateral impacts than apex impacts are appropriate for the use of foam liner helmets, whereas activities where the hazard is more likely to be falling objects call for web suspensions. For this reason motorcycle helmets are usually foam liner suspension and industrial "hard hats" are web suspension.
Fire service is an exposure to apex impacts and to lateral impacts. Further, fire service entails a high rate of exposure to relatively severe impacts. Falling and toppling objects are common and the fireman's ability to avoid them is hampered by low visibility conditions and equipment burdens. Firemen are also subject to injury of a vehicular nature. Consequently, a fireman's helmet should provide a high degree of attenuation of lateral and of apex impacts. The impact attenuation system of a fireman's helmet, unlike those for lower risk activities, must survive an impact to continue to protect him as the fire continues. A suspension which sacrificially destructs during attenuation is not appropriate for firemen. Severe impacts can cause the sacrificial failure of either web or foam liner suspensions.
In U.S. Pat. No. 4,286,339, there is disclosed a protection helmet, such as fireman's helmet which combines aspects of a web suspension with aspects of a foam liner suspension thereby obtaining the benefits of each form of suspension with the surprising result of apex impact attenuation markedly superior to either web suspensions or foam liner suspensions while providing lateral impact attenuation at least as good as foam liner suspensions. The chinstrap for such helmet assembly is rigidly affixed to the outer shell and is essentially unyielding to retain the protective helmet on the head when most needed, i.e., during a severe impact exposure. Concomitantly, such unyielding configuration resulted in fears of a broken neck or the individual being hung should the wearer fall through a floor or should the brim of the protective helmet place too much leverage on the wearer's neck. While certain prior art protective helmet assemblies are provided with a chinstrap assembly releasably attached to the protective helmet assembly, detachment of the helmet assembly from the user's head left the head of user unprotected against any subsequent contact with an object or against a stationary object.